Under exposing in Raw

[wadooz]

Hi Gang, just reading Andydo's thread about his under exposed Wedding shot. I use a Canon 450D and usually shoot in Raw. I was advised to deliberately underexpose in Raw to give me a faster shutter speed. The reason given was that it's dead easy to tweak it in Camera Raw or Lightroom 3 to bring out all the detail. Was this good advice or am I losing something by not getting it right in camera?
Cheers.
Martin.

[Cathus]

depends. RAW usually allows you to recover up to 2 stops of lost light but the more you try to recover the more the photo is degraded.

You would need to test whether recovering detail in RAW degrades the photo more or less than upping your ISO to achieve the same shutter speed. Both will degrade the photo, do test shots with your camera to see which works best.

Try upping the exposure on any shot in your RAW software by a stop at a time to see what effect this has on photo quality to give you an idea.

Personally, I think to get the best quality overall you need get it right in camera. This may require the use of filters for things like bright skies rather than underexposing the land & then degrading it in recovery just to get the sky OK. I think the saying is 'expose for the land, filter for the sky'.

[wadooz]

Thanks Cathus, I wish I'd asked the question earlier. I'd taken it as good advice and was underexposing all my shots just to get the sharper image. I hadn't realised the quality would suffer, thought it was my shaky hands. I'll stick to upping the ISO if need be in future. Thanks again.

[Cathus]

You need to get the balance, whilst you can recover detail from shadow if you underexpose, you can't recover detail from pure white in blown highlights. It's all part of the balancing act between shutter speed, aperture & ISO & then maximising what you have in software.

[wadooz]

So........ If the light is good, there's nothing to be gained by under exposing and upping the ISO. The shutter speed will be quicker but it won't necessarily be a better shot. I struggle with camera shake, I'm better off mastering my technique than changing settings to compensate. I'll just underexpose when really need to freeze the action. I took some shots last weekend using a monopod but wasn't too happy with the results. Now I know why. Probably should have posted this in the general beginner's forum too but never mind.
Thanks for your help.
Martin.

[Cathus]

If you're after faster shutter speeds then I'd up the ISO rather than underexpose, not do both as either way will introduce degradation so you don't want to have two lots of it.

You could do some test shots at home, you don't need to be shooting fast stuff, anything will do. Take a shot which is deliberately underexposed at say 1/250 sec or whatever (you could check the meter reading then dial in -2-3 stops of aperture), then take the same shot by upping the ISO so that it is correctly exposed at 1/250 sec (up the ISO by 2-3 stops), get them both in RAW and adjust them so they look the same exposure wise & see which one looks best.

[wadooz]

Thanks I'll try all that in the morning, it's getting a bit late now. If I can get my shots half as good as your aircraft shots I'll be very happy! And your Iphone shots are pretty damned good too! Just been looking at them in the other forum. Did you do much post processing? You must have a very steady hand 'cos there's no tripod and it's all live view at arm's length 'eh.
Well done.

[jet_kit]

Hi Martin,
Cathus is right, you cannot recover detail from blown highlights because there's nothing there, however you can tease detail out of underexposed areas. So, if in doubt underexpose, but not massively.
You need to look at the subject. If you're doing a landscape with loads of sky then highlight detail is going to be important, even if it means losing shadow detail. A grad ND filter will help here, but not necessarily solve the problem entirely. This is why most pro's opt for HDR to get the best from the highlights and the shadows.
If camera shake is a problem, and you're not alone, try practising a few techniques to improve the situation rather than just going for high ISO's and shutter speeds. 1. Make sure the camera has a stable platform - if that is you, stand with your feet about 18" apart. 2. Stand upright and let your pelvis relax, this will lock it into place. Unless there is a tree or building, or something you can lean on for added support. 3. Support the camera with your left hand, with the camera body on the heel of your hand and your fingers under the lens. Try to take all the weight on the left, leaving the right to locate the shot and press the shutter. 4. Tuck your elbows into your side. 5. Finally, don't jab the shutter - try rolling your finger over it rather than pressing down on it. Take a deep breath, let it out slowly then when it's about halfway out, hold it and fire.

[wadooz]

Thanks Chris, it's a cracking day so I'm heading off out to practice and experiment. I'm confident my shots will be much improved thanks to yours and Cathus's advice.
Cheers.
Martin.

[jet_kit]

Great Martin,
Let's see the results.